> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/client-interfaces/ecpg.md).

# Chapter 34. ECPG — Embedded SQL in C

**Table of Contents**

[34.1. The Concept](/client-interfaces/ecpg/ecpg-concept.md)

[34.2. Managing Database Connections](/client-interfaces/ecpg/ecpg-connect.md) : [34.2.1. Connecting to the Database Server](/client-interfaces/ecpg/ecpg-connect.md#ECPG-CONNECTING)

```
[34.2.2. Choosing a Connection](ecpg-connect.md#ECPG-SET-CONNECTION)

[34.2.3. Closing a Connection](ecpg-connect.md#ECPG-DISCONNECT)
```

[34.3. Running SQL Commands](/client-interfaces/ecpg/ecpg-commands.md) : [34.3.1. Executing SQL Statements](/client-interfaces/ecpg/ecpg-commands.md#ECPG-EXECUTING)

```
[34.3.2. Using Cursors](ecpg-commands.md#ECPG-CURSORS)

[34.3.3. Managing Transactions](ecpg-commands.md#ECPG-TRANSACTIONS)

[34.3.4. Prepared Statements](ecpg-commands.md#ECPG-PREPARED)
```

[34.4. Using Host Variables](/client-interfaces/ecpg/ecpg-variables.md) : [34.4.1. Overview](/client-interfaces/ecpg/ecpg-variables.md#ECPG-VARIABLES-OVERVIEW)

```
[34.4.2. Declare Sections](ecpg-variables.md#ECPG-DECLARE-SECTIONS)

[34.4.3. Retrieving Query Results](ecpg-variables.md#ECPG-RETRIEVING)

[34.4.4. Type Mapping](ecpg-variables.md#ECPG-VARIABLES-TYPE-MAPPING)

[34.4.5. Handling Nonprimitive SQL Data Types](ecpg-variables.md#ECPG-VARIABLES-NONPRIMITIVE-SQL)

[34.4.6. Indicators](ecpg-variables.md#ECPG-INDICATORS)
```

[34.5. Dynamic SQL](/client-interfaces/ecpg/ecpg-dynamic.md) : [34.5.1. Executing Statements without a Result Set](/client-interfaces/ecpg/ecpg-dynamic.md#ECPG-DYNAMIC-WITHOUT-RESULT)

```
[34.5.2. Executing a Statement with Input Parameters](ecpg-dynamic.md#ECPG-DYNAMIC-INPUT)

[34.5.3. Executing a Statement with a Result Set](ecpg-dynamic.md#ECPG-DYNAMIC-WITH-RESULT)
```

[34.6. pgtypes Library](/client-interfaces/ecpg/ecpg-pgtypes.md) : [34.6.1. Character Strings](/client-interfaces/ecpg/ecpg-pgtypes.md#ECPG-PGTYPES-CSTRINGS)

```
[34.6.2. The numeric Type](ecpg-pgtypes.md#ECPG-PGTYPES-NUMERIC)

[34.6.3. The date Type](ecpg-pgtypes.md#ECPG-PGTYPES-DATE)

[34.6.4. The timestamp Type](ecpg-pgtypes.md#ECPG-PGTYPES-TIMESTAMP)

[34.6.5. The interval Type](ecpg-pgtypes.md#ECPG-PGTYPES-INTERVAL)

[34.6.6. The decimal Type](ecpg-pgtypes.md#ECPG-PGTYPES-DECIMAL)

[34.6.7. errno Values of pgtypeslib](ecpg-pgtypes.md#ECPG-PGTYPES-ERRNO)

[34.6.8. Special Constants of pgtypeslib](ecpg-pgtypes.md#ECPG-PGTYPES-CONSTANTS)
```

[34.7. Using Descriptor Areas](/client-interfaces/ecpg/ecpg-descriptors.md) : [34.7.1. Named SQL Descriptor Areas](/client-interfaces/ecpg/ecpg-descriptors.md#ECPG-NAMED-DESCRIPTORS)

```
[34.7.2. SQLDA Descriptor Areas](ecpg-descriptors.md#ECPG-SQLDA-DESCRIPTORS)
```

[34.8. Error Handling](/client-interfaces/ecpg/ecpg-errors.md) : [34.8.1. Setting Callbacks](/client-interfaces/ecpg/ecpg-errors.md#ECPG-WHENEVER)

```
[34.8.2. sqlca](ecpg-errors.md#ECPG-SQLCA)

[34.8.3. `SQLSTATE` vs. `SQLCODE`](ecpg-errors.md#ECPG-SQLSTATE-SQLCODE)
```

[34.9. Preprocessor Directives](/client-interfaces/ecpg/ecpg-preproc.md) : [34.9.1. Including Files](/client-interfaces/ecpg/ecpg-preproc.md#ECPG-INCLUDE)

```
[34.9.2. The define and undef Directives](ecpg-preproc.md#ECPG-DEFINE)

[34.9.3. ifdef, ifndef, elif, else, and endif Directives](ecpg-preproc.md#ECPG-IFDEF)
```

[34.10. Processing Embedded SQL Programs](/client-interfaces/ecpg/ecpg-process.md)

[34.11. Library Functions](/client-interfaces/ecpg/ecpg-library.md)

[34.12. Large Objects](/client-interfaces/ecpg/ecpg-lo.md)

[34.13. C++ Applications](/client-interfaces/ecpg/ecpg-cpp.md) : [34.13.1. Scope for Host Variables](/client-interfaces/ecpg/ecpg-cpp.md#ECPG-CPP-SCOPE)

```
[34.13.2. C++ Application Development with External C Module](ecpg-cpp.md#ECPG-CPP-AND-C)
```

[34.14. Embedded SQL Commands](/client-interfaces/ecpg/ecpg-sql-commands.md) : [ALLOCATE DESCRIPTOR](/client-interfaces/ecpg/ecpg-sql-commands/ecpg-sql-allocate-descriptor.md) — allocate an SQL descriptor area

```
[CONNECT](ecpg-sql-connect.md) — establish a database connection

[DEALLOCATE DESCRIPTOR](ecpg-sql-deallocate-descriptor.md) — deallocate an SQL descriptor area

[DECLARE](ecpg-sql-declare.md) — define a cursor

[DECLARE STATEMENT](ecpg-sql-declare-statement.md) — declare SQL statement identifier

[DESCRIBE](ecpg-sql-describe.md) — obtain information about a prepared statement or result set

[DISCONNECT](ecpg-sql-disconnect.md) — terminate a database connection

[EXECUTE IMMEDIATE](ecpg-sql-execute-immediate.md) — dynamically prepare and execute a statement

[GET DESCRIPTOR](ecpg-sql-get-descriptor.md) — get information from an SQL descriptor area

[OPEN](ecpg-sql-open.md) — open a dynamic cursor

[PREPARE](ecpg-sql-prepare.md) — prepare a statement for execution

[SET AUTOCOMMIT](ecpg-sql-set-autocommit.md) — set the autocommit behavior of the current session

[SET CONNECTION](ecpg-sql-set-connection.md) — select a database connection

[SET DESCRIPTOR](ecpg-sql-set-descriptor.md) — set information in an SQL descriptor area

[TYPE](ecpg-sql-type.md) — define a new data type

[VAR](ecpg-sql-var.md) — define a variable

[WHENEVER](ecpg-sql-whenever.md) — specify the action to be taken when an SQL statement causes a specific class condition to be raised
```

[34.15. Informix Compatibility Mode](/client-interfaces/ecpg/ecpg-informix-compat.md) : [34.15.1. Additional Types](/client-interfaces/ecpg/ecpg-informix-compat.md#ECPG-INFORMIX-TYPES)

```
[34.15.2. Additional/Missing Embedded SQL Statements](ecpg-informix-compat.md#ECPG-INFORMIX-STATEMENTS)

[34.15.3. Informix-compatible SQLDA Descriptor Areas](ecpg-informix-compat.md#ECPG-INFORMIX-SQLDA)

[34.15.4. Additional Functions](ecpg-informix-compat.md#ECPG-INFORMIX-FUNCTIONS)

[34.15.5. Additional Constants](ecpg-informix-compat.md#ECPG-INFORMIX-CONSTANTS)
```

[34.16. Oracle Compatibility Mode](/client-interfaces/ecpg/ecpg-oracle-compat.md)

[34.17. Internals](/client-interfaces/ecpg/ecpg-develop.md)

This chapter describes the embedded SQL package for PostgreSQL. It was written by Linus Tolke (`<linus@epact.se>`) and Michael Meskes (`<meskes@postgresql.org>`). Originally it was written to work with C. It also works with C++, but it does not recognize all C++ constructs yet.

This documentation is quite incomplete. But since this interface is standardized, additional information can be found in many resources about SQL.

***

原文：[PostgreSQL 18.6 Documentation](https://www.postgresql.org/docs/18/ecpg.html)（英文原文，待翻譯）


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